My understanding in regard to the AC Gasket is that it needs to be snug but not overly tight. If too tight will deform the gasket and cause a leak.
Now I could be all wet, but that's what I have picked up from other RV Forums.
Michelle & Ann
2018 Chevy 3500HD Crew Cab High Country DRW, D/A, 2016 RW39MB, Dual ACs, Auto Level, Auto Sat Dish, Stack W/D, King Sleep #, 17.5" Sailuns w/Disc, MORryde IS & Pin, Comfort Ride Hitch, 5.5 Onan, Res Fridge & Induction Cook Top